Filters Reduce TSS & NTU for Power Plant Process Water
Shepard Energy Centre, owned by Enmax and Capital Power Corp., is located in Calgary, AB, Canada. It began operating in March 2015 and is capable of generating more than 800 MW of electricity to Alberta residents using natural gas. The facility utilizes two combustion turbines featuring a combined-cycle technology and processes waste heat through a steam turbine to generate electricity. This process makes Shepard approximately 30% more efficient than traditional coal-fired plants, and it reduces overall fuel costs. The Shepard plant is not only more efficient than a coal-generated facility, but also better for the environment by emitting less than half the CO2 emissions per MWh. Sulphur dioxide and nitrogen dioxide emissions also are reduced.
The Solution
The facility uses up to 7.7 million gal per day (mgd) of reclaimed wastewater from the city of Calgary’s Bonnybrook Wastewater Treatment Plant. This is the first application of reclaimed water for power production in Alberta. The majority of this water is used for cooling tower water and boiler feed water.
Enmax and Capital Power chose to install three eight-disk AquaDisk cloth media filter units to help in this process. Effluent from the Bonnybrook Wastewater Treatment Plant is pumped through a nine-mile-long pipe to the Shepard Energy Centre. Water then passes through the three AquaDisk cloth media filters before being sent to the cooling tower. Filtration is key in preventing solids accumulation in the cooling tower.
Filter Process
Water from the Bonnybrook Wastewater Treatment Plant enters the filters and flows by gravity through the cloth media of the stationary hollow disks. The filtrate exits through the hollow shaft, which supports the individual disks and flows to the effluent channel. As solids accumulate on the surface of the media, the water level surrounding the disks rises. Once a predetermined level is reached, the disks rotate and the media surface is automatically vacuum-backwashed clean. Heavier solids settle to the bottom of the tank and are then removed using a solids manifold. Both backwash and solids wastewater are sent back to the wastewater treatment plant.
Design Characteristics
The AquaDisk filters remove total suspended solids and reduce turbidity to protect the heat exchangers from clogging. This, in turn, reduces energy consumption and, in severe cases, prevents plant shutdown.
Shepard Energy Centre is now Alberta’s largest gas-fueled electricity generation facility.